The present invention relates to a magnetic head for recording and/or reproducing signals on and/or from a magnetic tape at a high density and a method of making such a magnetic head.
Magnetic tapes for video tape recording have heretofore been composed of a backing material coated with a thin magnetic film of magnetic oxide particles. To meet demands for signal recording at a higher density, there have been developed in the recent past magnetic tapes having a magnetic coating of fine metal particles or a deposited metal film. These metallic-coating tapes have a higher coercivity than that of conventional oxide-particle tapes. However, prior magnetic recording heads, that is, heads with ferrite oxide cores, cannot magnetize the metallic-coating tapes sufficiently as the cores tend to be easily saturated.
Various magnetic heads for high-density recording have been developed which include metal cores made by materials such as Sendust or amorphous materials having a saturation magnetic flux density higher than that of magnetic oxides. It is known that magnetic heads having Sendust cores undergo a reduced permeability in a high-frequency region due to an eddy-current loss and are less resistant to wear than conventional oxide heads, and amorphous heads suffer from a poor high-frequency response because of the heat treatment or high-temperature heating that the core is subjected to in the manufacturing process.
Therefore, it is necessary that magnetic heads of Sendust or amorphous materials be constructed in order to eliminate the foregoing problems. One conventional high-density magnetic head includes a pair of magnetic cores of Sendust, one having a winding slot, which are butted together with a thin gap-defining shim interposed therebetween and are ground into a thin web having a thickness of over ten microns. The cores are sandwiched between nonmagnetic plates having winding slots and bonded thereto, with a tape-contacting surface ground to a desired finish. This type of magnetic head has been disadvantageous in that with the magnetic cores being of a small cross-sectional area, the head has a poor playback efficiency. Since the cores are thinned by being ground after the gap has been defined, the gap is liable to get spread widely open or broken during the grinding process. Furthermore, the nonmagnetic plates which cover the cores prevent the gap depth from being measured correctly while the tape-contacting surface is being ground, with the result that the gap depth cannot be precisely defined.
Another conventional magnetic head is composed of a pair of magnetic oxide cores of ferrite held in abutting relation and having magnetic bodies of Sendust only at the tape-contacting surface. Since the cores have a greater cross-sectional area than that of the magnetic head as described above, the head has a better playback efficiency. However, the magnetic path in the head contains junctions between the Sendust bodies and the oxide cores, the junctions giving rise to an unwanted magnetic loss which fails to achieve a sufficiently high playback efficiency.